Cupola furnace



Feb. 19, 1946. w. M. McNl-:IL

CUPOLA FURNACE A Filed sept'. 19, 1941 2 Sheets-Sheet 2 2z 26M M h.

retenait-en 19, i946` CUPOLA FURNACE William M. McNeil, Wheaton, Ill.,assigner to United States Gypsum Company, Chicago, Ill., a corporationof Illinois Application September 19, 1941, Serial No. 411,504

14 Claims.

This invention relates to methods of and apparatus for the production ofmineral melt, and has reference more `particularly to a combinationsteam generating furnace and cupola which is useful for the productionof mineral wool.

In the production of mineral wool by the blowing of molten mineralmatter with steam or other gas, it is customary to charge a mixture ofcoke and mineral matter into a cupola and to effect the melting of themineral matter by the combustion of the coke in the cupola. The coke andmineral matter are charged into the cupola in rather large pieces inorder to enable combustion gases readily to passthrough the fuel bed. Ithas in the past been impractical to use cheap coal as a fuel since, onheating, the coal has a tendency to become plastic and packs within thecupola so that air and combustion gases will not pass through the fuelbed. Also coal usually contains a high percentage of volatile matter anda large portion of the heat in the coal is not eectively utilized in thecupola because the combustible volatile matter has a tendency to distilloff and to pass up the stack. Also, the cupolas of the prior art havegenerally been charged by hand shoveling thereby materially increasingthe labor cost of operating the same.

An object of this invention, therefore, is to provide a combinationcupola and furnace which will successfully burn coal as a fuel.

Another object of this invention is to provide a furnace cupola in whichfine or coarse mineral matter may be melted to form a molten slag forblowing into mineral wool.

Another object of this invention is to provide a furnace cupola in whichthe volatile matter is completely burned with ther liberation of heatwhich is utilized to produce steam for blowing molten slag into mineralwool or for other purposes.

Another object of the invention is to provide a furnace cupola in whichthe coal is preheated to distill off the volatile matter and to producepieces or chunks of coke and sintered mineral matter which may bedischarged into a cupola thereby permitting free passage of air andcornbustion gases through the fuel bed in the cupola.

A further object of the invention is to provide a furnace cupola inwhich a mixture of coal and mineral matter'is fed automatically into thefurr provide a two stage process of producing mineral wool which issimple and economical.

Further and additional objects will appear from the followingdescription, the accompanying drawings, and the appended claims.

In accordance with one embodiment of this invention, an apparatus hasbeen provided, (1) for subjecting a mixture of carbonaceous material,such as coal, and mineral matter, to a preliminary heating step in orderto drive off the combustible volatile matter from the carbonaceousmaterial and to cause a coalescence of the carbonaceous material andmineral matter, (2) for discharging the resulting lumps of consolidatedcarbonaceous material and mineral matter into a cupola whereby themineral matter is melted, and (3) for finally discharging the mineralmelt from the cupola in a continuous stream. The cupola is provided withsteam generating tubes in association with a steam boiler positioned ina combustion chamber above the cupola for providing high pressure steamfor disintegrating the molten stream of mineral matter into mineralwool. The volatiles distilled from the mixture of carbonaceous materialand mineral matter are burned in the combustion chamber above the 7provided for the preparation of a melt of mineral matter from a mixtureof finely divided mineral matter and carbonaceous material, such asslack coal. This melt may be blown by a high pressure steam jet into amineral wool product. However, if desired, other products may beprepared from th melt, such as deiluorinated phosphate rock which issuitable for use as a fertilizer. rination may be effected by passing aquantity of steam over the mixture of a fluorine-containing phosphateand a carbonaceous material undergoing combustion before introductioninto the cupola. Alternative or supplementary deuorination may also beeffected by treating the phosphate melt discharged from the cupola withsteam at low pressure to form pellets of a deiluorinated phosphate whichlatter may be used as a fertilizer.

For a more complete understanding of this invention, reference will nowbe had to the drawings .forming a part of this specification, in whichDefluothe pit I2 and delivering the mixture to a hopper |6 positionedabove a moving chain grate stoker I8 positioned adjacent the lower oorof a combustion chamber 20. Air ducts 22, controlled by dampers 24, arepositioned below the upper reach of the chain grate stoker I8 and amanifold 26 connects a blower 28 to the ducts 22 for supplying air forcombustion purposes to and through the mixture of slack coal and mineralmatter on the chain grate stoker I8. The chain grate stoker I8 moves inthe direction indicated by the arrow in Fig. 1 towards a chute 30 whichis positioned above a cupola 32 and is so arranged that the materialdeposited on the stoker I8 from .the bin I6 will be discharged into thetop of the cupola 32.

The cupola 32 comprises an elongated upright chamber having an ovalcross-section which is provided with side walls lined with a pluralityof vertically extending steam generator tubes 34 connected to an uppermanifold 38 and a lower manifold 38. As most clearly shown in Fig. 3,refractory cement 40 extends between the tubes 34, and a layer ofmineral wool 42 extends between a metal shell 44 and the refractorycement 40.

As shown most clearly in Fig. 1, the upper end of the cupola 32 opensinto the combustion chamber 20 so that gases from the cupola and airfrom the ducts 22 passing through the grate stoker I8 may be combined.In the upper portion of the combustion chamber 20 is positioned a boiler45 mounted within a setting 48. A plurality of boiler tubes 50 extendlongitudinally through the boiler 46 and provide passageways between thecombustion chamber 20 and a stack 52, thereby providing means fordischarging hot combustion gases from the combustion chamber.Surroundlng the stack 52 are preheating jackets 54, 56, and 58 (see Fig.2), having a blower 60 associated therewith for forcing intake airthrough a duct 62, which is connected to the jacket 54, and ducts 64 and66 which are connected to jackets 54, 56 and 58 in seriesl A duct 68extends from the jacket 58 to a bustle box 10 which surrounds a medialportion of the cupola 32. Tuyres 'I2 are provided for injectingpreheated air from the bustle box to the lower portion of the cupola 32to accelerate the combustion of the coke therein, whereby the mineralmatter associated therewith is fused. Adjacent a lower edge of the oorof the cupola 32 is located a spout or port 14 through which the melt isdischarged to a point near a steam blowing nozzle 'I6 whichdisintegrates the mineral melt into mineral wool. The nozzle 18 ispositioned to discharge the blown fibers to a blow chamber .18 throughan opening 80 whereby the fibers are deposited on a conveyor 82 to forma mat 84 of mineral wool.

In order to provide cold make-up Water for the steam generating systemof the apparatus, an intake water pipe 88 connects with pipes 88 passingin series through a refractory arch 80 which extends obliquely into thecombustion chamber 20 above the cupola 32, .This arch serves not only tocarry the pipes 88 for preheating the make-up water but also lengthensthe path of travel of the gases of combustion from thecupola into thecombustion chamber so as to make the combustion more complete. A pipe 82is provided for removing the preheated water from the pipes 88 withinthe arch 80 and connects with a cylinder 94 of a water pump which isoperated by a steam cylinder 98. A pipe 98 having a check valve |00extends between the cylinder 94 and a circulating pipe |02 fordischarging the preheated water into the lower manifold 38 surroundingthe cupola 32. A blow-oil valve |04 is provided in the manifold 38 todischarge sludge from the system' when necessary. A steam pipe |08connects the upper manifold 38 of the cupola 32 and the boiler 48. Wateris withdrawn from the boiler 46 by a pump |08 through a line ||0 andcirculated through the line |02 to the lower manifold 38 of the cupola32. As shown, a. steam drumr I2 is provided in the top of the boiler 48and a steam pipe ||4 leads therefrom for conducting high pressure steamto the wool blowing nozzle 16. A branch steam pipe 6 leads from the pipe||4 to the steam cylinder 96, the flow of steam through said pipe I6being controlled by a valve II8. A branch pipe |20 controlled by valve|22 leads from the steam pipe ||4 to the duct 88 so that steam, ifdesired, may be introduced into the cupola 32 through the tuyres 'I2 inorder to assist in certain chemlca1 reactions such as the deuorinationof phosphate rock.

A charging door |24 is provided in the furnace setting 48 above thecupola 32 so that fuel may be manually added to said cupola if desired.A clean-out door |26 is also provided in the setting 48 above the arch90.

In th'e operation of the above described apparatus, coal slack andmineral matter are dumped into the pit I2 and the mixture is carried bythe bucket conveyor I4 to the hopper I5 and is discharged through asuitable gate onto the chain grate stoker I8. The mineral matter mixedwith the coal slack may be granulated slag, small size rock, coarse sandor gravel, clay, ph'osphate rock, or similar material. Other forms ofcarbonaceous material may be substituted for the slack coal if desired.For example, under certain conditions it may be desirable to employpetroleum coke or a heavy petroleum pitch. The relative amounts ofmineral matter and carbonaceous material may be adjusted so that thecombination of the charged mineral matter combined with v the ash ofth'e carbonaceous material produces a melt having the desiredcomposition. The mixture of carbonaceous material and mineral matter onthe chain grate stoker I8 is continuously advanced toward the chute 30.The high temperature within th'e combustion chamber causes the volatilematter to be distilled from the slack coal or other carbonaceousmaterial on the stoker surface and the volatile matter admixed with airpassed through the stoker from the ducts 22 burns within the combustionch'amber 20. These hot products of combustion pass through the tubes'50of the tube boiler 46 to generate steam therein and they thereafter passout through the stack 52. 'I'h'eheating and partial distillation of thematerial on the chain grate stoker I8 causes the slack coal or othercarbonaceous material to carbonize to form a coke which coalesces withthe mineral matter to form relatively large pieces 2,398,231 or chunksof a mixture of coke and mineral matair passing into the cupola throughthe tuyresl 'I2 from the bustle box l0, this air having been preheatedin th'e stack jackets 54, 56 and 58 that are connected thereto ashereinbefore described. The fused mineral matter flows in a streamthrough the port I4 and is blown into mineral wool by the steam nozzle16. 'I'he mineral wool sintered mixture of .coke and mineral matter, and

fra second stage in which the pieces of this mixture deposits on theconveyor 82 in the blow chamber I8 in the form of amat 84. Y u

Hot water under pressure circulates in the system from .the boiler 46through the pipe IIII, the circulating pump -I08, the pipe |82, themanifold 38, the steam generating tubes 34, the manifold 36 and the pipeI 86. Cold make-up water is supplied as needed through the pipe 86, th'epreheating pipes 88 ln the arch 90, the pipe 92, the water pump 94, and1 the pipe 88, into the pipe |82. Steam passes from the steam drum I I2associated with the boiler 46 through' the pipe II4 to the nozzle 'I6and through the pipe H6 to the steam cylinder 96. The steam generated inthe steam generating tubes 34 of the cupola 32 passes through thepipe'IIl6 to th'eboiler 46 along with the-circulating water.

YThe carbonaceous mixture that is deposited on the stoker ,I8 from thebin I6 should be spread in a relatively thin layer over the uppersurface of the stoker to permit the free passage of air -th'erethroughfrom the ducts 22, and to permit conveying systems may be employed t0effect this result.

As most clearly indicated in Fig. 3, the melting chamber* within thecupola 32 has an oval crosssection and the cupola is disposed withrespect I to the stoker so that the maximum diameter of the cupolaextends transversely to the direction of movement/of the stoker. Thesintered mass of carbonaceous material and mineral matter is thus morereadily deposited within the cupola and a more even temperature withinthe cupola is. obtainable than would be the case if the cross sectionthereof were circular.

From the above description it will appear that a process' and apparatushave been described for producing a stream of mineral melt the flow ofwhich from the cupola remains substantially constant or may be regulatedas desired. The rate of flow of the melt may be controlled by regulatingthe speed ofA the belt conveyor I4 and the chain grate stoker I8, themineral matter in the mixture being supplied to the top of the cupola.at substantially the same rate as it is desired to withdraw the meltfrom the bottom thereof through the spout 14.

It is apparent that'the cupola furnace of this invention carries out atwo stage process, viz: an initial stage in which the volatile matter isdistilled from the coal to produce large pieces of a into mineral wool.

are completely burned'at a high temperature to produce moltenv mineralmatter which is blown The coking step is carried out with the c'oallying on the stoker in a shallow layer so that it can be readily heatedand coalesced and so that air for combustion can readily pass throughthe sintering mixture. The second or melting stepis carried out whilethe large pieces are maintained in a comparatively deep column. lIn thesecond step, the fuel is in the form of pieces of coke which readilypermitthe passage of the preheated air and combustiongases therethroughand the carbonaceous material has passed the plastic stage Where it willtend to coalesce within the cupola. Thus fusion of the mineral matter ismore readily` effected in the cupola. 'I'he process is especiallyadvantageous because of the low cost of the materials which may be ustedincluding coal fines, or even slack coal having a high ash content, andfine mineral matter which is ordinarily discarded as waste. The cupolafurnace also produces its own'steam for blowing purposes, and utilizesmost of the waste heat so that stack gases are discharged at the lowestpossible temperature. The mixture of coal and mineral matter isautomatically fed to the furnace thus greatly reducing the labor ofoperation incident to hand firing heretofore used.

The apparatus is suited for a variety of uses other than the productionof mineral Wool. For instance, it may be used for the smelting of ores,such as iron ore. As another example, gypsum might be included in themineral mixture so that sulfur dioxide and sulfuric acid becomes one ofthe by-products. 'I'he apparatus might also be used for thedefluorination of phosphate rock in the production of phosphatefertilizer or even elemental phosphorus. In this type of reaction, thesteam introduced into the cupola enters into the reaction to accomplishthe deiluorination of the rock. Low temperature steam maybe used' at thenozzle 'I6 in defiuorination so that pellets of fused phosphate rock areproduced instead 0f wool. Deuorination may also be effected by mixingsteam with the air which is passed through the mixture of mineral matterand carbonaceous material on the stoker I8.`

It will be recognized that the fuel and mineral matter may be thoroughlymixed before it is initially charged into the receiving pit. This mixingmay be effected in any type of mixing machine (not shown) such as onewhich is useful for mixing concrete. In such case, the fuel and mineralmatter may be stored in separate storage bins (not shown) and withdrawnin desired quantities and supplied to the mixer. The resulting mixturehaving a predetermined composition may then be charged to the receivingpit I2 and thereafter passed through the cupola furnace as hereinbeforedescribed.

While a particular embodiment of this invention is shown above, it willbe understood, of course, thatthe invention is not to be limitedthereto, since many modifications may be made, and it is contemplated,therefore, by the appended claims, to cover any such modifications asfall within the true spirit and scope of this invention.

I claim: l

l. The process of producing fused mineral matter by a continuous processwhich comprises admixing mineral matter with a carbonaceous fuelcontaining volatile matter in substantial quan titles, passing theresulting mixture on a conveyor through an enclosed combustion zonewherein assumez Stoker within said setting and spaced from said saidvolatile matterA is burned from the fuel and a sintered mass of mineralmatter and coke-like material is formed, discharging the resultingsintered mass in lump form into a separate high temperature melting andoxidizing zone wherein said coke-like material is burned thereby fusingsaid mineral matter, and substantially continuously removing said fusedmineral matter from said oxidizing zone.

2. The method of producing a stream of molten mineral matter, whichcomprises moving a mixture of solid carbonaceous fuel initiallycontaining volatile matter in substantial quantities and solid mineralmattei' in a shallow layer through an enclosed combustion zone, heatingsaid layer therein under oxidizing conditions so as to distill and burnthe volatile matter from said fuel and to produce substantially largepieces of a sintered mixture of coke-like material and mineral matter,introducing said pieces into a vertial combustion chamber provided withmeans for forcing combustion-supporting gases therethrough, completlngthe combustion of the carbonaceous fuel in said chamber whereby toproduce gaseous products of combustion and fused mineral matter, andwithdrawing said fused mineral matter in a stream from the bottom ofAsaid chamber.

3. The method of continuously producing a melt suitable for blowing intomineral wool which comprises continuously moving a mixture of coal andpotentially fusible mineral matter in a shallow layer in an enclosedcombustion zone, heating said layer under oxidizing conditions thereinso as rto distill and burn volatile matter from said coal and to producesubstantially large pieces of a sintered mixture of coke and mineralmatter, continuously introducing said pieces into a combustion chamberyprovided with positive means for forcing combustion supporting gasestherethrough, and completing the combustion of the coke in said chamberto produce gaseous products of combustion and fused mineral matter.

4. The process of producing fused mineral matter by a continuous processwhich comprises admixing a finely divided carbonaceous fuel containingvolatile matter in substantial quantities with finely divided mineralmatter, continuously advancing the resulting mixture on a conveyorthrough a primary combustion and heating chamber whereby the fuel isincompletely burned to distill off the volatile matter and a sinteredmass of mineral matter and coke-like material is formed, continuouslydischarging said sintered mass in lump form into a separate hightemperature melting cupola wherein said coke-like material is burnedthereby fusing said mineral matter, and continuously removing said fusedmineral matter from said cupola.

5. The method of heat treating a substance, which comprises continuouslymoving a mixture of carbonaceous fuel and mineral matter in a shallowlayer, subjecting said layer to oxidizing conditions so as to distilland burn volatile matter from said mixture and to produce a sinteredmixture of coke and mineral matter, assembling said sintered mixture ina combustion chamber,

passing preheated air through said assembled mixture whereby to burnsaid coke and continuously to produce a mass of fused mineral matter,and continuously withdrawing said fused mineral matter from saidcombustion chamber.

6. In an apparatus of the class described, a furnace setting, a boilerwithin said setting, a

boiler, a cupola associated with said stoker,

`means for supplying a mixture of solid fuel and mineral matter to saidstoker to be sintered and incompletely burned, means for supplying acombustion-supporting gas to the mixture on said stoker, means forremoving said sintered mixture from said stoker into said cupola, saidcupola having Walls comprising a series of vertically arranged watertubes, means for completing the combustion of carbon in said mixturewithin said cupola to form fused mineral matter, and means forcirculating water between said boiler and the water tubes of said cupolawhereby to generate steam.

7. In an apparatus of the class described, a housing, a chain gratestoker in said housing, a receiving pit, a feed hopper associated withsaid stoker, conveyor means for delivering a mixture of solid. fuel andmineral matter from said pit to said hopper, said hopper being arrangedto deliver a shallow layer of said mixture on said Stoker, means forsintering and partially burning the mixture on said stoker, a cupola,means for delivering said mixture to said cupola to be completely burnedto form molten mineral matter, and means for withdrawing said fusedmineral matter from said cupola.

8. An apparatus of the character described which comprises a firstcombustion chamber, a conveyor within said chamber, means for supplyinga mixture of solid fuel and mineral matter to said conveyor, means forsupplying combustion-supporting gases to the mixture on said conveyorwhereby said mixture is sintered and the fuel therein is incompletelyburned, a second combustion chamber opening into said first combustionchamber for receiving the sintered mixture from said conveyor, means forsupplying additional combustion-supporting gases to said secondcombustion chamber completely to burn the fuel in the sintered mixturetherein whereby to melt said mineral matter, and means for dischargingthe molten mineral matter from said second combustion chamber.

9. An apparatus of the character described which comprises a firstcombustion chamber, a stoker within said chamber, means for supplying amixture of solid fuel and mineral matter to said stoker whereby saidmixture is advanced within said chamber, means for supplyingcombustion-supporting gases to the mixture on said Stoker whereby tosinter the mixture and incompletely to burn the fuel in said mixturethereby liberating hot combustion gases, a second combustion chamberpositioned adjacent the discharge end of said stoker communicating withsaid rst .combustion chamber, means for supplying additionalcombustion-supporting gases to said second combustion chamber completelyto burn the fuel in said mixture therein whereby to melt said mineralmatter, means for withdrawing combustion gases from said apparatus, an`dmeans for discharging the molten mineral matter from said secondcombustion chamber.

10. An apparatus of the character described which comprises a firstcombustion chamber, a boiler positioned in the upper reaches of saidchamber, a stoker within said chamber spaced from said boiler, means forsupplying a mixture of solid fuel and mineral matter to said stoker`whereby said mixture is advanced within said chamber, means forsupplying combustion-supporting gases to the mixture on said stokerwhereby to sinter the mixture and incompletely to burn the fuel in saidmixture thereby liberating hot combustion gases, a second combustionchamber positioned adjacent the discharge end of said stokercommunicating with said first com- 'bustion chamber, means for supplyingadditional combustion-supporting gases to said second combustion chambercompletely to burn the fuel in V 11. An apparatus of the characterdescribed' which comprises a first combustion chamber, a boilerpositioned in the upper reaches of said chamber, a stoker Within saidchamber spaced jacent the discharge end of said stoker adapted toreceive said lumps, means for supplying a combustion-supporting gas tosaid melting chamber whereby said fuel in themixture is burned to meltsaid mineral matter and to produce hot combustion gases, said meltingchamber being open to said primary chamber whereby the hot combustiongases pass to the latter lto assist in from said boiler, means forsupplying a mixture of solid fuel and mineral matter to said stokerwhereby said mixture is advanced within said chamber, means forsupplying combustion-supporting gases to the mixture on said stokerwhereby to sinter the mixture and incompletely to burn the fuel in saidmixture thereby liberating hot combustion gases, a, second combustionchamber positioned adjacent the discharge end of said stokercommunicating with said rstcombustion chamber, means for supplyingadditional combustion-supporting gasesto said second combustion chambercompletely to burn the fuel in the sintered mixture whereby to melt saidmineral matter and to form additional hot combustion gases, means foradmixing the hot combustion gases from each combustion chamber, meansfor passing the combined hot combustion gases into heat exchangerelationship withsa/id boiler prior-to discharge from the apparatus,means for discharging the molten mineral matter from said secondcombustion chamber, steam-generating tubes associated with said secondcombustion chamber, means for circulating Water and steam from. saidboiler to said steam-generating tubes, and means for dischargingVgenerated steam from said boiler.

12. An apparatus for the continuous production of a melt suitable forblowing into mineral wool, from mineral matter and a nely dividedcarbonaceous fuel containing volatile matter in substantial quantities,which comprises, a primary sintering and combustion chamber, a stokerfor continuously passing a mixture of said min'- eral matter and saidfuel in a shallow layer through said sintering and combustion chamberwhereby the mixture is sintered to form large lumps, a vertical meltingchamber'positicned adthe sintering operation, and means for continuouslydischarging molten mineral matter in a stream from the melting chamber'as rapidly as it is formed. l

13. An apparatus for the continuous production of a melt lsuitable forblowing into mineral wool, from minerall matter and finely divided coalwhich comprises, a primary sintering and combustion chamber, a steamboiler within said chamber, a, stoker for continuously advancing amixture of said mineral matter and said coil in a shallow layer throughsaid chamber whereby said mixture is sintered to form large lumps of amixture of coke-like material and mineral matter, a

supporting gas to said melting chamber whereby said coke-like materialin the mixture is burned open to said primary chamber whereby the hotcombustion gases pass to the latter t0 assist in the sinteringoperation, means for circulating water and steam from thesteam-generating tubes to the boiler, means for supplying make-up waterto the boiler, and means for continuously discharging molten mineralmatter in a stream from the melting chamber as rapidly as it is'formed.I

14. The method of heat-treating a mixture containing a. finely divided4fuel and a fusible material by a continuous method which comprisesadvancing the mixture in a shallow layer on a conveyor through a firstcombustion zone under conditions controlled to permit said fuel to beincompletely burned to produce sintered lumps of a mixture of coke-likematter and fusible material, dischargingv said lumps as rapidly as theyare formed from the conveyor into a second combustion zone, passing acombustion-supporting gas into said second zone to burn the coke-likezone.

' WILLIAM M. McNEIL.

Certificate of Correction Patent No. 2,395,231. Februarylg, 1946. I

WILLIAM M. MCNEIL It is hereby certified that errors appear in theprinted specification. of the above numbered patent requiring correctionas follows:` Page 1, second column, line 41, for th melt read the melt;page 5, second column, line 19, claim 13, for coil read coal; and thatthe said Letters Patent should be read with these corrections therein ithat the lsame may conform to the record. of the case in the PatentOfiice.

Signed and sealed this 14th day of May, A. D. 1946.

[SEAL] LESLIE FRAZER,

Ffirs Assiste/ni Commissioner of Patents.

